The invention relates to the field of intravascular devices, and particularly to a guidewires suitable for procedures such as angioplasty and/or stent deployment, and the like.
In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is first advanced in the patient""s vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient""s coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with inflation fluid one or more times to a predetermined size at relatively high pressures so that the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom.
After such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate of angioplasty alone and to strengthen the dilated area, physicians now normally implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel or to maintain its patency.
Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter, which is very similar in many respects to a balloon angioplasty catheter, and expanded within the patient""s artery to a larger diameter by inflating the balloon. After stent deployment, the balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated herein by reference. Thus, stents are used to keep open a stenosed vessel, and strengthen the dilated area by remaining inside the vessel. Instead of first using one catheter to dilate the body lumen and a second catheter to deploy the stent after the dilatation, the stent may be mounted on a balloon catheter and deployed at the same time the balloon is inflated to dilate the stenotic region.
In both of these procedures the physician has to make an estimate of the length of the stenotic region which is to be dilated or into which a stent is to be deployed in order to assess the length of the balloon to be used for the dilatation or the length of the stent to be deployed. Heretofore, it has been suggested to provide a variety of markers on the distal portion of the guidewire and/or catheters in order to make the length determination of stenosis. Many of these prior efforts involve providing various spacings between multiple radiopaque markers on the distal portion of the guidewire to allow the physician to make the length determination fluoroscopically with the guidewire in position within the artery and the markers traversing the stenotic region. However, due to the two dimensional nature of the fluoroscopy, these prior methods have not always been very accurate because of the orientation of the stenosis and the guidewire within the stenosis is not always suitable for an accurate length determination.
The invention is generally directed to an improved method and devices for the measuring of a distances within a patient""s body lumen such as the length of stenosis within a patient""s coronary arteries.
The invention involves the use of a guidewire which has at least one marker or other location indicia on the distal portion of the guidewire which is observable (e.g. fluoroscopically) by the physician. The guidewire is positioned within the patient""s body with the distal marker being placed at or adjacent to one end of the intracorporeal location to be measured and then the guidewire is repositioned so that the same distal marker is placed at or adjacent to the other end of the intracorporeal location. The portion of the guidewire which extends out of the patient""s body moves the same distance as the distal marker is moved between the ends of the intracorporeal location to be measured and measurement of the extracorporeal movement of the guidewire is determined in order to determine the length of the intracorporeal location.
The movement of the proximal portion of the guidewire which extends out of the patient can be measured in a variety of ways. For example, ruler-like indicia, which can be seen and/or felt, e.g. transverse ridges or grooves, can be placed on the surface of the proximal extremity of the guidewire which extends out of the patient. To make the internal measurement, the guidewire is located within the patient""s body so that the distal marker on the guidewire is positioned at or adjacent to one end of the intracorporeal location to be measured. The first external position of an indicia on the proximal end of the guidewire is then referenced with respect to an external reference point, e.g. the proximal end of the guiding catheter adapter. When the guidewire is moved to position the distal marker at the other end of the intracorporeal location, the indicia on the proximal end of the guidewire likewise moves, and the distance it moves is the intracorporeal distance measured. The physician or other operator can determine the distance within the two intracorporeal locations by visual or manual reference to the relative movement of the ruler-like indicia to the external point of reference.
Other methods can be used to determine the distance traveled by the guidewire when changing the location of the distal marker. A wheeled distance sensing member may be pressed into engagement with the surface of the proximal end of the guidewire extending out the patient. The wheel of the distance sensing member rotates as the guidewire is moved and this rotation can be converted into a suitable distance readout. Similarly, an electro-optical system may be utilized to measure the distance the guidewire moves. A wide variety of other methods may be employed to make the distance measurement. These distance measuring systems must be referenced to a suitable substrate, e.g. the adapter on the proximal end of the guiding catheter, so that the axial movement of the guidewire can be properly detected. To ensure that the distal position of the guidewire is not lost, it is preferred to first position the distal marker on the guidewire at the proximal intracorporeal location and then advance the guidewire distally within the body lumen until the distal marker is adjacent to the distal intracorporeal location. The reverse procedure can be employed, i.e. place the distal marker at the distal end of the stenosis first and then at the proximal end of the stenosis, but in this case the guidewire must then traverse the lesion again which can be time consuming. However, by first placing the distal marker at the most distal end of the lesion and then withdrawing the guidewire proximally to move the distal marker to the proximal end of the lesion ensures that any slack present in the guidewire will be removed and thereby ensure an accurate measurement.